It is known to manufacture tailgate structural elements from steel, for example lateral uprights surrounding the rear screen, or a lower horizontal cross member arranged in the lower part of the rear screen. This type of steel structural element generally consists of an elongated hollow body with a closed cross-section to stiffen the tailgate and arrange a rear screen bonding track which is attached to the structural element. It is also possible to manufacture plastic structural elements, not requiring a closed cross-section and having for example a greater depth and equivalent stiffness. In this case, the cross-section of the structural element can be U-shaped with an opening facing the outside of the vehicle and subsequently closed by the tailgate screen. In these two types of structural element, the space delimited by the structural element and optionally the screen is a closed inaccessible space.